John M. Drugli

Aspects of testing and selecting stainless steels for seawater applications

Abstract Relatively recent failures in seawater systems of highly alloyed (i.e., pitting resistance equivalent [PREN] > 40) stainless steels (SS) have highlighted the issue of corrosion testing and safe-use limits. Three aspects of testing and selection of SS for seawater application were reviewed: relevancy of the electrochemical test methods, the quality control system, and the importance of repassivation. A potentiostatic test for assessment of critical pitting (CPT) and crevice (CCT) temperatures was analyzed with respect to its ability to generate data relevant to chlorinated seawater systems. CPT seemed valid as safe-use limits, but the CCT determined were too high. A modified test approach was proposed. Generally, significant scatter in CCT and CPT values was registered, focusing on the importance of statistical experimental approach and data analyses. Recommendations were made on use of the ASTM G 48 test as a quality control method. The validity of critical pitting and crevice indices was analyze...

The behaviour of corrosion-resistant steels in seawater: A review

Abstract Research on stainless steels in seawater carried out during the last decade is briefly reviewed. With natural seawater it is shown that the formation of a biofilm on the surface has an important influence on the local corrosion initiation tendency and propagation rate at temperatures up to 30–40°C. In chlorinated seawater the tendency to local corrosion initiation is even stronger, but the propagation rate is typically less than in natural seawater. Ageing of the surface is shown to have a distinct influence on the initiation tendency, and this observation may be utilized during the start-up of a chlorinated seawater handling system in order to minimize the risk of local corrosion. Finally, testing methods for corrosion in welds and crevices are briefly discussed and some typical results from such testing are shown. The critical corrosion initiation temperature and a lower critical repassivation temperature for crevices are dealt with.

Critical Crevice Temperature for High-Alloyed Stainless Steels in Chlorinated Seawater Applications

Eleven high-alloyed stainless steels (SS) were tested for application in chlorinated seawater. Critical crevice temperatures (CCT) were determined using a potentiostatic test method. Results were evaluated in terms of the critical crevice index (CCI) value of the alloys and compared to results of duplicate specimens in other tests.

Testing of Stainless Steel Welds for Various Applications

Abstract In several investigations, potentiostatic, potentiodynamic, and standard ASTM-G48 test techniques have been used to evaluate the corrosion properties of stainless steel welds. Testing for various applications is discussed, and test methods are recommended. Tests should always be performed for the least resistant parts of a system, usually as-welded field welds and/or narrow crevices. The 6% FeCl3 test solution is often more severe than the real environment because of the higher potentials obtained. Therefore, excessively low, critical temperatures are measured. Testing according to ASTM-G48 seems to be relevant for highly alloyed stainless steels for exposure to oxidizing chloride solutions that raise the potential in the range of 400 to 700 mV SCE. In order to perform realistic testing relevant to practical applications, the maximum free potential obtained in real environments should be known. Potentiostatic tests, using the maximum potential for the actual environments, are recommended for test...

A Short Duration Test Method for Prediction of Crevice Corrosion Rates on Stainless Steels

Abstract The aim of the present work has been to develop a short duration test method by which it is possible to: (1) determine the necessary conditions for crevice corrosion, and (2) predict the corrosion rate in active crevices for different area ratios between free surface and crevice. The method consists of determination of cathodic and anodic polarization curves on separate cathode (free surface) and anode (crevice) specimens, respectively, by certain applied procedures. The results from short duration tests on three different stainless steels in chloride solutions have been compared with results from long duration tests, and fairly good agreement has been found. It is thought that the short duration method can be applied for determination of the most significant crevice corrosion properties. With minor adjustments, the method is also applicable for aluminum alloys in chloride solutions.